Aging proceeds in all organs of the entire body. In the observable skin, especially in the facial surface on which people tend to focus attention, wrinkles and fine wrinkles formed with advancing age are annoying many middle-aged and older people, especially women, all over the world. Conventionally, there has been demand for cosmetics for alleviating wrinkles, however, the mechanism regarding aging and wrinkles has not been largely clarified. Hence, in the conventional cosmetics, moisturizers such as glycerin, biochemical products such as mucopolysaccharides and collagen, and synthetic polymer products have been blended merely to keep moisture of the skin for alleviating wrinkles.
The method of classifying wrinkles into three groups (i.e. a graphic wrinkle, a crinkle, and a linear wrinkle) on the basis of distinction in appearance is known (refer to Non-patent literature 1). The moisturizing function of the aforementioned components contained in the conventional cosmetics is effective only for limited crinkles, that is the wrinkles owing to dryness, formed by rapidly losing water. A graphic wrinkle is a deep and crisscross wrinkle formed in the skin of exposed area such as facial surface and neck, and sunlight gives a considerable effect on the graphic wrinkle. A cutaneous change, as represented by a wrinkle induced by sunlight, is called “photo aging”. For photo aging, the method of irradiating UVB on the back of a hairless mouse, proposed by Kligman et. al., has been established as a method using an animal model (refer to Non-patent literature 2). For details, by initially irradiating the back of hairless mouse (e.g. HR-1 or skh-1) with a low irradiance of UVB (290 to 320 nm wavelength) and gradually increasing the irradiance level to irradiate it with 4 J or more UVB in total for 10 weeks or more, the barrier function of the stratum corneum is decreased and a deep wrinkle which is perpendicular to the midline is induced.
Linear wrinkles, also called expression wrinkles, are so-called “crow's feet” in the outer corner of one's eye or fine wrinkles formed in an area which is constantly moved, such as around mouth or between the eyebrows. The linear wrinkle becomes prominent in their thirties or later. This kind of wrinkle is formed by skin deformation owing to facial expressions, and it may be formed even at an early age depending on a frequency of such deformation. However, the decreased barrier function of the stratum corneum, caused as a result of repeated drying of the skin, is known as a major factor that the linear wrinkle becomes apparent (refer to Non-patent literature 3).
It is difficult to alleviate a graphic wrinkle or a linear wrinkle by applying mere moisturizers, and decreased barrier function of the skin gives an affect on these wrinkles as a wrinkle formation factor. Wrinkles can be formed on the back of a mouse by repeatedly damaging the skin barrier on the back of the mouse by tape-stripping (refer to Non-patent literature 4). In a hairless mouse having atopic-like skin, which is developed as a model for decreased barrier function of the skin, dryness in the skin and formation of wrinkles were observed (refer to Non-patent literature 5).
As described above, there is a close relation between decreased barrier function of the skin and formation of graphic wrinkle or linear wrinkle. Normal growth and appropriate differentiation of epidermal keratinocytes are important for barrier function of the skin. It is known that, for atopic dermatitis which has abnormal growth and differentiation of epidermic cells, squamous cell carcinoma antigen (hereinafter mentioned as SCCA) is increased abnormally (refer to Patent Literature 1). Additionally, it is known that UV irradiation makes growth and differentiation of epidermic cell abnormal and increase the SCCA expression. For example, it is reported that, for human, the facial skin having wrinkles owing to constant exposure to sunlight has higher SCCA expression compared with the body skin having no exposure to sunlight (refer to Patent literatures 1 and 2).    Non-patent literature 1: Kligman A M, Br. J. Dermatol. 113:37-42 (1985).    Non-patent literature 2: Kligman L H et al., J. Am. Acad. Dermatol. 21:623-631 (1989). Non-patent literature 3: Imokawa G., et al. Fragance Journal, 20(11); 29-42 (1992). Non-patent literature 4: Matsunaga M, British J. dermatol., 156 (5); 884-891 (2007). Non-patent literature 5: Makiura M et al., J Int Med. Res. 32:392-399 (2004), Non-patent literature 6: Katagiri C., J. C. B., 172(7); 983-990 (2006). Patent literature 1: WO2006/098523. Patent literature 2: Japanese Unexamined Patent Publication 2005-27343